The present invention relates generally to pneumatic tires, and specifically to high performance tires adapted for use in snow as well as on dry and wet pavement.
High performance tires have been characterized by relatively large and stiff traction elements to reduce squirm and provide better handling characteristics. The tires of the present invention have smaller traction elements than comparably sized prior art high performance tires, while still retaining the lateral stiffness of the larger traction elements for good handling. However, the new tires have reduced circumferential stiffness that provides better snow traction than prior art high performance tires.
Tires according to the preferred embodiment of the present invention have been tested for snow traction and showed very good results when compared to commercially available high performance tires. The test results are shown in Tables I and II. In this test a rating of 100 represents the performance of a standard rib-type of tire in snow specially prepared to be as nearly uniform as possible for each test. All of the tires in Table I are of a size P 225/60 R 15.
TABLE I __________________________________________________________________________ Tire Eagle VR60 Eagle VR60 Eagle GT Tire of Eagle M & S (Carved) (Molded) (Carved) Invention (Molded) Rating 62/59 78/78 98 112 132 (Forward/reverse (Forward/reverse (Non- (Non- (Non- This is a This is a directional) directional) directional) directional tire) directional tire) __________________________________________________________________________
The named tires used in the comparative tests are manufactured by The Goodyear Tire & Rubber Company, and are illustrated on pages 41-42 of the 1986 TREAD DESIGN GUIDE which is published by Tire Guides, Inc. It can be seen that the tire according to the preferred embodiment of the present invention had better snow traction than the commercially available high performance tires tested, with the exception of the Eagle M&S which is a "snow tire" designed specifically for use in mud and snow.
The results of the comparative test shown in Table II are similar to those shown in Table I.
TABLE II __________________________________________________________________________ Tire P195/60R15 P205/60VR15 P215/60R15 P205/70HR14 Eagle VR60 Eagle GT Tire of Invention Eagle M & S (Molded) (Molded) (Carved) (Molded) Rating 77/44 101 140 144 (Forward/reverse (Non-directional) (Non-directional) (Non-directional) This is a directional tire) __________________________________________________________________________
Tests for comparing the handling characteristics of a tire according to the preferred embodiment to a Goodyear Eagle GT (which is a commercially successful high performance tire) showed the new tire to have handling characteristics that are substantially equal overall to those of the Goodyear Eagle GT. The tires in this test were of a size P205/60 R 14.
It may be concluded based upon the test results available at the time that a patent application is being filed that a tire according to the present invention provides wet and dry handling characteristics that are substantially equal overall to those of prior art high performance tires, while providing better snow traction than those same tires.
There is provided in accordance with one aspect of the present invention a pneumatic tire comprising: (a) a pair of axially spaced apart annular beads; (b) a radial ply carcass structure extending between said beads with an axially outer portion of the carcass structure folded about each of said beads: (c) a circumferentially extending belt structure disposed radially outwardly of said carcass structure in a crown region of the tire: said belt structure having a pair of axial edges: and (d) a ground engaging tread portion of elastomeric material disposed radially outwardly of said belt structure and extending circumferentially thereabout, said tread portion having a pair of axially spaced apart tread edges, said tread portion having at least four straight grooves therein which extend circumferentially thereabout, two of said circumferentially extending grooves being disposed between each of said tread edges and a mid-circumferential plane of the tire, the axially outermost circumferential groove on each side of the mid-circumferential plane communicating with the axially outermost circumferential groove on the other side of the mid-circumferential plane by means of two series of curved grooves, the grooves of said first series of curved grooves extending between said axially outermost circumferential grooves in a first direction that is inclined with respect to the mid-circumferential plane and the grooves of said second series of curved grooves extending between said axially outermost circumferential grooves in a second direction that is inclined with respect to the mid-circumferential plane opposite to said first direction, each of said curved grooves having a centerline which has a point of inflection of curvature located substantially at the mid-circumferential plane of the tire, each groove of said first series of curved grooves intersecting at least one groove of said second series of curved grooves on each side of the mid-circumferential plane, each of said curved grooves communicating with each of said tread edges by means of drainage grooves extending from said axially outermost circumferential grooves to the nearest tread edge in a substantially axial direction, an axially inner end of each of said drainage grooves being aligned circumferentially with an axially outer end of one of said curved grooves: said circumferential grooves, said first and second series of curved grooves and said drainage grooves cooperating to define a plurality of circumferentially extending series of individual traction elements.
There is provided in accordance with yet another aspect of the invention a pneumatic tire comprising: (a) a pair of axially spaced apart annular beads: (b) a radial ply carcass structure extending between said beads with an axially outer portion of the carcass structure folded about each of said beads: (c) a circurferentially extending belt structure disposed radially outwardly of said carcass structure in a crown region of the tire, said belt structure having a pair of axial edges; (d) nylon cords extending in a substantially circumferential direction located radially outwardly of at least one layer of said belt structure in the area of its said axial edges for restricting the displacement of the axial edges of said belt structure; and (e) a ground engaging tread portion of elastomeric material disposed radially outwardly of said belt structure and means for restricting and extending circumferentially thereabout, said tread portion having a pair of axially spaced apart tread edges, said tread portion having at least four straight grooves therein which extend circumferentially thereabout, an equal number of said circumferentially extending grooves being disposed between each of said tread edges and a mid-circumferential plane of the tire, the axially outermost circumferential groove on each side of the mid-circumferential plane communicating with the axially outermost circumferential groove on the other side of the mid-circumferential plane by means of two series of curved grooves, the grooves of said first series of curved grooves extending between said axially outermost circumferential grooves in a first direction that is inclined with respect to the mid-circumferential plane and the grooves of said second series of curved grooves extending between said axially outermost circumferential grooves in a second direction that is inclined with respect to the mid-circumferential plane opposite to said first direction, each of said curved grooves having a centerline which comprises a continuous curve which has a point of inflection of curvature located substantially at the mid-circumferential plane of the tire, each groove of said first series of curved grooves intersecting on each side of the mid-circumferential plane a number of grooves of the second series of curved grooves equal to the number of circumferential grooves located on that same side of the mid-circumferential plane, the centerline of each groove of said first series of curved grooves intersecting the centerline of one groove of said second series of curved grooves in the axially outermost circumferential groove on one side of the mid-circumferential plane and intersecting the centerline of another groove of said second series of curved grooves in the axially outermost circumferential groove disposed on the other side of the mid-circumferential plane, each of the axially outer ends of each of said curved grooves being circumferentially aligned with a drainage groove which extends in a substantially axial direction from the respective axially outermost circumferential groove to the nearest tread edge; said circumferential grooves, said first and second series of curved grooves and said drainage grooves cooperating to define a plurality of circumferentially extending series of individual traction elements, the ratio of circumferential length to axial width of said traction elements in a footprint of the tire being greatest for the traction elements that intersect the mid-circumferential plane and progressively less for each subsequent series of traction elements disposed between two of said circumferential grooves as the axial distances of the series from the mid-circumferential plane increases, the traction elements of each circumferentially extending series which is axially interposed between two of said circumferential grooves have a generally triangular shape when viewed looking radially inwardly towards said tread structure, and the traction elements of the circumferentially extending series which are disposed axially outwardly of the axially outermost circumferential groove on each side of the mid-circumferential plane have a generally rectangular shape when viewed looking radially inwardly towards said tread structure.
There is provided in accordance with yet another aspect of the invention a pneumatic tire comprising: (a) a pair of axially spaced apart annular beads; (b) a radial ply carcass structure extending between said beads with an axially outer portion of the carcass structure folded about each of said beads; (c) a circumferentially extending belt structure disposed radially outwardly of said carcass structure in a crown region of the tire; said belt structure having a pair of axial edges: (d) nylon cords extending in a substantially circumferential direction located radially outwardly of at least one layer of said belt structure in the area of its said axial edges for restricting the displacement of the axial edges of said belt structure; and (e) a ground engaging tread portion of elastomeric material disposed radially outwardly of said belt structure and means for restricting and extending circumferentially thereabout, said tread portion having a pair of axially spaced apart tread edges, said tread portion having at least four straight grooves therein which extend circumferentially thereabout, an equal number of said circumferentially extending grooves being disposed between each of said tread edges and a mid-circumferential plane of the tire, the axially outermost circumferential groove on each side of the mid-circumferential plane communicating with the axially outermost circumferential groove on the other side of the mid-circumferential plane by means of two series of curved grooves, the grooves of said first series of curved grooves extending between said axially outermost circumferential grooves in a first direction that is inclined with respect to the mid-circumferential plane in a first direction and the grooves of said second series of curved grooves extending between said axially outermost circumferential grooves in a second direction that is opposite to said first direction, each of said curved grooves having a centerline which comprises a continuous curve which has a point of inflection of curvature located substantially at the mid-circumferential plane of the tire, each groove of said first series of curved grooves intersecting on each side of the mid-circumferential plane a number of grooves of the second series of curved grooves equal to the number of circumferential grooves located on that same side of the mid-circumferential plane, the centerline of each groove of said first series of curved grooves intersecting the centerline of one groove of said second series of curved grooves in the axially outermost circumferential groove on one side of the mid-circumferential plane and intersecting the centerline of another groove of said second series of curved grooves in the axially outermost circumferential groove disposed on the other side of the mid-circumferential plane, each of the axially outer ends of each of said curved grooves being circumferentially aligned with a drainage groove which extends in a substantially axial direction from the respective axially outermost circumferential groove to the nearest tread edge; said circumferential grooves, said first and second series of curved grooves and said drainage grooves cooperating to define a plurality of circumferentially extending series of individual traction elements, the ratio of circumferential length to axial width of said traction elements in a footprint of the tire being greatest for the traction elements that intersect the mid-circumferential plane and progressively less for each subsequent series of traction elements disposed between two of said circumferential grooves as the axial distances of the series from the mid-circumferential plane increases, the traction elements of each circumferentially extending series which is axially interposed between two of said circumferential grooves have a generally triangular shape when viewed looking radially inwardly towards said tread structure, and the traction elements of the circumferentially extending series which are disposed axially outwardly of the axially outermost circumferential groove on each side of the mid-circumferential plane have a generally rectangular shape when viewed looking radially inwardly towards said tread structure.